The definition of a micro-grid varies throughout the civilian and military expeditionary energy community. The various micro-grid definitions can be characterized by their scope of service and ownership structure. Scope of service could range from small commercial individual facilities that use micro-grids to substations whose loads are supplied with micro-grids and a fully mobile military micro-grid. The definition varies for end-use customers, landlords, municipal utilities and investor-owned utilities. Each of these owners is looking for a different configuration value from a micro-grid and has a different “sweet spot” for the scope and definition of service. Industry, military and academia such as DTE Energy, the Consortium for Electric Reliability Technology Solutions (CERTS), the Electric Power Research Institute (EPRI), the European Research Project Cluster, Northern Power, the Gas Technology Institute (GTI), ENCORP, the National Renewable Energy Laboratory NREL, GE, Lawrence Berkeley National Lab, Project Manager (PM) Mobile Electric Power (MEP) and the US Army Corps of Engineers all have differences in functionality, and hence a difference in the definition of a micro-grid. The expeditionary or mobile type of micro-grid discussed in this disclosure is very different than what would be used commercially in that the grid size can be considered one power supply (e.g., a mobile generator, vehicle export AC or DC, battery storage AC or DC, or fuel cell) distributing to one shelter, or to a larger, but limited group of shelters. This arrangement can be enlarged to supply power to larger camps and related appliances used within a camp, although a larger camp may include a set of individual micro-grids within the same camp, that are not tied to one another.
Historically an expeditionary military fielded military micro-grid is an electrical distribution system connecting any combination of single, multiple soft or hard wall shelters, maintenance shelters, electric kitchens, showers, washer/dryers, and personnel equipment such as hair dryers, radios, and televisions as an example. This distribution system's electrical power is supplied by one or more mobile diesel generators of various kW outputs that are generally positioned around the outside perimeter of the distribution system.
An example of a fielded micro-grid would be for a Bare Base troop bed-down operation. Force Provider for the Army and Harvest Eagle and Harvest Falcon for the Air Force are AC engine generator supplied micro-grid users. The Navy and Marine Corps have constructed permanent and quasi-fixed bare base facilities that also use micro-grid generator power.
The number of individual micro-grids that are needed can range from a small Patrol Expeditionary Camp (PEC), for example, with three shelters and a shower using two micro-grids and two generators for energy supply, distribution infrastructure, to a medium (e.g., 150 man) camp with housing, feeding, laundry, shower systems and Environmental Control Units (ECU e.g. a military hardened AC that use six micro-grids and six generators), to large (e.g., 5,000 man) camps with full size complementary infrastructure such a larger kitchens, laundries, heated showers, food refrigeration and freezers, employing many ECUs that would use prime power (larger not easily towable generators) with the amount of individual micro-grids broken down into sections to supply the camp. The power and energy consumption control methods described below pertain to the various individual micro-grids, and configurations that operate individually within the same camp or foot print that uses mobile generation and/or renewable energy. This disclosure may also provide fuel savings when used with prime power equipped camps. The difference between mobile and prime power is, prime power utilizes 100 KW or larger generators, buried high voltage cable with transformers serving large sections of the camp and is somewhat permanent in design losing its expeditionary value. Mobile expeditionary generators are sized to be towed with smaller vehicles, such as the Humvee, and are used to operate small individual micro-grids within the camp. Fielded expeditionary micro-grid use, as discussed above, is currently configured with many separate stand alone micro-grids in use within the camp, operating each micro-grid as an island within the camp to insure adequate power to each of the individual grids.
Expeditionary military micro-grids are ever changing dynamic systems that when fielded are arranged in many configurations to facilitate the various camp assets, locations and type of camp operation. Inherent to a mobile micro-grid, is the effect of changing energy loads of a small number of appliances, where ECUs laundry and showers can cause the electrical energy on its micro-grid to drop. Typically, excess generator energy capacity is provided on each grid to accommodate such on/off cycling and peak demand loads. Unlike large commercial energy providers, the grouping of individual small size micro-grids in one expeditionary camp makes it impractical to define a fuel-efficient base load. For instance, the addition of one air-conditioner can cause a momentary brown out of one grid during the inrush energy load. A mobile military micro-grid is typically not staffed with operators monitoring system loads and capacity, and consequently the many individual micro-grids comprising one camp may not operate at optimum power generation and fuel efficiency.
Current art employs two methods of generator power supply side management techniques, both maintaining a percentage of reserve capacity above the base load. The first method is the most basic of control and is the legacy and current configuration extensively used today in a mobile micro-grid. The generators are started manually and left running as long as the power is needed. This may be a single generator or a plurality of generators operating on one common micro-grid, or a plurality of mobile generators each operating it respective micro-grid. One disadvantage of using many individual micro-grids is due to the fact that the generators are not able to communicate and load share with each other or with generators of different sizes. Another disadvantage is the inability to connect individual micro-grids into larger distribution networks. The second prior art method of generator capacity control is one in which the mobile generators can communicate with each other to curtail or add generator operation as load and reserve conditions warrant. This communication provides load sharing between generators of the same or different sizes and provides the power control to connect or consolidate individual micro-grids. This commercially available control function will likely be incorporated in future expeditionary camps, in one form or another, to interconnect what are now stand alone micro-grids to automatically turn on and off generators. In this arrangement, a designated main Generator Set Controller (GSC) may broadcast a control signal to other GSC equipped generators when engine start or connection to buss is desired to maintain reserve capacity (e.g., percentage of reserve power has been exceeded by the growing base load). Reacting to the random appliance starting inrush and operational consumption that increased the base load, tripping the reserve energy setting of the designated main GSC. This event causes the GSC to add reserve capacity to re-establish the same base load to reserve capacity profile. This power control method provides better fuel savings than letting the generators run but still requires excess capacity to be on line continuously adjusting the excess spinning capacity as the camp base load increases or decreases. Though this method of distributed mobile generator control will reduce the amount of stand alone micro-grids, reduce the amount of individual generators running, and lower the fuel use, substantial capacity is still maintained to prevent brownout or equipment shutdown due to low power.
A deficiency is this control method is the inability to incorporate new energy supplies such as vehicle export and non-engine derived energy, such as renewable or stored battery energy, in a plural power supply environment.
Another disadvantage of this prior art method is the necessity of maintaining excess energy on line or in standby to be instantly ready (spinning) to operate a mobile micro-grid and is one of the main causes of fuel inefficiency.
Another disadvantage is the inability to predict or preplan power supply requirements in relation to energy consumption. This directly contributes to the inefficient use of fuel, energy, and/or other resources such as maintenance and logistics.
Due to the very small size of the mobile micro-grid another disadvantage when programming the generator controller for distribution, is the issue of what energy level is established to insure each of a grid's supply functions such as base load, load following, or peak power in any efficient manner. The inability to predict or preplan power supply requirements in relation to energy consumption directly contributes to the inefficient use of fuel, energy, and/or other resources such as maintenance and logistics.
Another inefficient shortcoming is the inability of the prior art systems to select from different generator capacities and non mobile generator energy supply sources such as renewables.
Another deficiency is that the mobile micro-grid is of such small size (low capacitance) that there is no average rise or reduction in demand, as appliances are turned on, because an instant response is required necessitating the operator to program higher reserve and surge capacity, increasing the spinning reserve capacity and wasting fuel.
Another inefficient shortcoming is the inability to sync phases between mobile generators and stored energy when the load can be carried by stored energy and the generators are restarted for larger loads.
Another inefficient shortcoming is a lack of communication based on a pre-communicated consumption appliance profile of resistive, inductive, or capacitive load energy required before appliance operation to forewarn the supply side to select the best fuel efficient method of power supply combinations before the individual appliance is allowed to run.
Yet another inefficient shortcoming of the prior art systems is the inability to load share diesel-operated generators with fuel cell generation, vehicle export power and renewable energy sources such as wind, solar, and energy storage systems.
Yet another inefficient shortcoming is the inability to ping the micro-grid to ascertain the supply, base load and inrush energy needed to operate the associated micro-grid.